1. Field of the Invention
The invention relates to a process for guiding in space an instrument arranged at the free end of an articulated arm and to an apparatus for performing the process.
In measuring technology, in material processing, and in particular in medicine, it is frequently the case that three-dimensional free-form surfaces on deformable or inhomogeneous specimens and the like have to be measured or processed. Various processes are as a rule made use of for guiding the measuring or processing instrument along the respective space curves, surfaces, or spatial regions which are to be investigated, in which processes the instrument is arranged at the free end of an articulated arm, and the instrument is moved in a predetermined range of movement by relative pivoting or moving of the individual arm sections.
2. Discussion of Relevant Art
Thus it is known, for example, in the field of microsurgery, and in particular neurosurgery, to cause an instrument which is located at the free end of such an articulated arm to move along a given path curve. The path curve is planned and predetermined before the operation in this case, with reference to the diagnostic results from nuclear spin tomography or computer tomography. The surgeon causes the instrument to travel during the operation by means of an actuating unit, for example a joystick or the like, connected to the control device of the articulated arm drive. The surgeon thus always obtains a mostly optical feedback as to whether or not he is on the predetermined path.
The guiding of the instrument along the predetermined path curve thus takes place here directly by the surgeon. On the one hand, this entails the disadvantage that the travel of the instrument during the whole operation requires a particularly high degree of concentration on the part of the surgeon, or increases the time required for the operation, and small inadvertencies or weakening of concentration can lead to considerable deviations from the predetermined path curve, with possibly serious consequences. On the other hand, control by means of a joystick entails a loss of the surgeon's direct tangible contact with the instrument. A consequence of this is that movements which are not restricted to the two main directions of motion (forward/backward, left/right) of the joystick partially require complex control movements, which require a relatively long working time and high concentration during the operation and therefore provoke operating errors.
In other processes, which are mostly carried out with known industrial robots, the predetermined path curve, etc., is traveled according to a previously programmed course, without this course being influenced by an operator. The instrument is indeed hereby relatively exactly guided along the predetermined path curve, but there is a disadvantage in that deviations in the geometry of the body to be processed or to be investigated with the instrument cannot, or can only at great expense, be sensed and compensated. Thus such processes are not suitable for microsurgery, for example, in which the surgeon must be able to react to any complications due to deviations or changes in the tissue occurring after the planning of the path curve.